Production of lubricating oil components of high viscosity index



July 21, 1959 R. w. B. JOHNSTON PRODUCTION OF LUBRICATING OIL COMPONENTS OF HIGH VISCOSITY INDEX Filed Aug. 16, 1955 umbro ,omo-.5mm

TNVENTOR ROBERT w.B. JOHNSTON BY: WQMWW Hls ATTORNEY United States Patent() PRODUCTION F LUBRICATING OIL COMP()- NENTS OF HIGH VISCOSI'I'Y INDEX Robert W. B. Johnston, Houston, Tex., assignor to Shell Development Company, New York, N.Y., a corporation of Delaware Application August 16, 1955, Serial No. 528,800

8 Claims. (Cl. 208-96) This invention relates to a process for producing lubricating oils, and particularly the production of mineral lubricating oils of high quality, including high viscosity index.

Heretofore, it has been the general practice to recover high quality mineral lubricating oil components from those crude oils and fractions thereof in which they occur naturally in economically recoverable proportions. It is generally recognized that considerable selection is required in order to secure proper crude stocks in adequate supply to meet the ever-increasing demands for high qualitylubricating oils. As the proportion of parailnic crude oil available for processing decreases and the proportion of naphthenic, and particularly of mixed naphthenic and asphaltic base crudes increases, the demands on processing techniques increase in order to recover the smaller AEn 2,895,903 Patented July 21, 19,59

ICC

oil fraction. However, the relatively small proportion of lubricating oil components present in the catalytic cracking heavy gas oil militates seriously against the commercial recovery of the lubricant components. Furthermore, the recoverable lubricating oil is a low viscosity oil, such as about a 100 to 150 SUS at 100 F. viscosity oil.

It is a principal object of the present invention to provide an improved'process for the production of mineral lubricating oils. A more specific object is to provide a process for the production and recovery of a higher proportion of lubricating oil from a crude petroleum oil and fractions thereof. A further object is to provide an improved process for the production and recovery of higher viscosity lubricating oils from a petroleum oil than heretofore obtained therefrom. The foregoing objects will be better understood and others will be apparent from the proportion of paranic components of lubricating chardetailed description of the invention, which will be made with reference to the accompanying drawing in which the sole gure is a diagrammatic flow sheet of the practice of the invention.

It has now been found'that lubricating oils of high quality can be obtained in increased amount from high molecular weight petroleum fractions, by a low conversion cracking of the oil stock at an elevated cracking ternperature with the formation of lubricating oil components and of highly carbonaceous products, separation of the oil and condensed carbonaceous material, and separation of highly saturate components in the higher boiling portion of the separated oil from highly aromatic components by selective extraction, thereby recovering a quality saturate lubricating oil.

In accordance with the present invention, oils which contain naturally only a relatively small proportion` of liquid paraiiins of lubricating viscosity and which contain substantial proportions of asphaltic, or asphalt precursor,

materials are cracked, preferably catalytically, at a low the undesirable ones in virgin stocks is not practical by solvent extraction because of the wide variety of types of compounds present. Furthermore, the relative solubilities of the various types present donot ybear any exact correspondence to the qualities which are desired in them as lubricants.

As a consequence, oils which contain a marginal proportion of desired components ofV different types and which contain undesirable components of intermediate solubility characteristics cannot be extracted economically to obtain a satisfactory yield of an oil of suitable quality. This is particularly true of certain oils of a more naphthenic and aromatic character.

It has been proposed recently to recover lubricating oil components of good quality from the heavy gas oilfraction of the product stream from the conventional catalytic cracking of virgin heavy gas oil. .Although the catalytic cracking operation is primarily for the production of gasoline, small proportions of high viscosity index light lubricating oil components are present in the heavy gas conversion level to produce further quantities of lubricant parailinic hydrocarbons while converting a portion of the highly. aromatic components to highly carbonaceous material kand reducing the concentration of -non-paranic compounds of intermediate solubilitycharacteristics iin selective solvents.

The present invention is applicable particularly to the production of lubricating oils from heavy crude fractions or residual oils which are highly aromatic and naphthenic in character, such as heavy oils containing a large proportion of highly condensed polycyclic hydrocarbons. It is especially useful in connection with the production of gas oil from such heavy oil stocks where the gas oil is Aproduced to be used as feed stock in a subsequent cracking process for the production of motor fuel stocks, either thermal or catalytic processes, or both, and particularly catalytic cracking. E

Various types of low conversion cracking can be utilized in the process of the invention, here again either thermal or catalytic, or both. A particularly useful process is one which may be designated catalytic decarbonization. This process is usually designed to process a heavy, asphaltic or tarry crude, or residual fractions therefrom, such as a reduced crude therefrom with a heated iluidizecl solid catalyst of low activity, such as a partially spent synthetic silica-alumina gel catalyst or a natural aluminum silicate material, such as a suitable clay, to elect a low conversion of material to light products such as gasoline hydrocarbons and lighter while effecting substantial dealkylation of alkylated polycyclic components and consequent condensation of dealkylated polycyclics to highly carbonaceous materials. An enhanced yield of distillate oil is thereby obtained and the dealkylated polycyclic components are removed on the catalyst as asphaltenes and other highly carbonaceous oil-insoluble materials, in addition to coke which is formed in the process.

The low conversion catalytic cracking may be carried out as a separate catalytic decarbonization process for the production of a maximum amount of liquid distillable hydrocarbons to be used as feed stock to a conventional catalytic, cracking operation. Onthe other hand, it may be a rst stagey operation in a multiplestage catalytic cracking process, such as in a two-stage catalytic cracking. Such desired low-Conversion cracking can be readily obtained in, for example, a irst stage riser-type disperse phase catalytic cracking operation which is operated at low contact times. In such case, the heaviest distillate fractionscan be separated from the heavy gas oil and the former processed for the recovery of the saturate lubricating oil components while the extracted aromatic cornponents are blended with the remainder of the gas oil as catalytic cracking feed for lgasoline production, or used as high boiling aromatic solvent, fuel oil cutter stock, and the like.

In order to demonstrate the utility of a low-conversion catalytic cracking process for the production from a residual stock of distillate material from which a good recovery of usefu1 lubricating oil components can be made, a West Texas straight run residue (WTSRR), the residue from topping the crude to remove gas oil having a 90% end point of approximately 325 C., was subjected to a dispersed-catalyst-phase cracking in an upilow, short contact time, catalytic cracking zone at a conversion of 32.9%. The heavy gas oil produced amounted to 42.3% of the charge. The operating data are shown in Table I.

WTSRRzWestTexas straight run residue. 1' Synthetic silica-alumina gel (l0-15% alumina) with surface area 76 square meters per gram.

The heavy gas oil was distilled, and the distillation cuts were reblended to produce a so-called 100 distillate (distillate from which a lube rafnate of 100 SUS at 100 F. is obtainable upon solvent extraction) and a residue which was found to correspond in molecular weight range to a conventional 250 distillate from an East Texas lube crude. Properties of these two blends are shown in Table Il. The yields of 100 and 250 distillate were 16.2% and 21.8%. respectively, basis West Texas straight run residue. Data are also shown for the recovery and properties of high quality saturated lubricating oil fractions from the two fractions, showing viscosity indices of 109.5 and 119.7, respectively. Analyses according to hydrocarbon types are shown under Composition, showing total saturates contents of 50.4 and 48.8% wt., respectively.

TABLE II Yield of lube ozl from heavy gas all from catalytic decarbomzatzon Process Data.:

Charge to CDP WTSRR Conversion (-450 F., percent wt.)- 32. 9 HGO, percent wt. of charge 42. 3

Gas Oil 100 Dist Residue Product Properties:

Distillation Cut Numbers l-7 7-28 Boiling Range, F 615-672 642-765 765+ API 25. 5 18.1 Viscosityat 100 F., SUS 73. 59 272. 4 F.) ai'. 210 F 36. 28 64. 74 Viscosity Index.-. 64. 5 67. 8 Percent wt. of HGO. 10. 8 38.4 50.8 Percent wt. of WTSRR 4. 3 16. 2 21. 8 Saturate Cut:

Yield, percent wt. of traction 62.8 58. 0 Viseosityat 100 F.. SUS 03. 84 123. l (130 F.) at 210 F 35. 55 50. 70 Viscosity Index 109. 5 119. 7 Congealing Point, F 64 105 Composition, percent wt.:

Alkenes 19. 9 13. 6 Non-condensed Cycloalkanes... 17.9 20.5 Condensed Cyeloalkanes 12.6 14. 7

Total Saturates 50. 4 48. 8

Olens (by Chromatography and Brornine Number) 7. 7 4. 5 15. 7 13.7 7. 3 4. 8 7.2 5. 6 3. 5 3.2 1. 2 3. 5 0.0 2.1 Total Sulfur Compounds 7.0 11.8 Resins 0.0 2.0

The distillates prepared from the cracked oil were treated in a one-stage batch extraction using a 1.8 phenolto-oil ratio. The raiinates were dewaxed at plant conditions used commercially for East Texas oilv of similar Extraction cost is directly related to the concentration of the, undesired aromatic components in the extraction charge. The high aromatic content of West Texas crude and even higher aromatic content of the oils from lowconversion cracking of West Texas crude would appear to increase extraction costs. Although this is true for the straight run stock, it does not turn out to be the case for thestock from the low-conversion cracking. This is illustrated by the. data in Table III. The oils for which properties are shown in Table Il-I; were prepared, as previously stated, in"r a one-stage batch extraction using a 1.8 phenolto-o`il ratio. In comparison with refinery plant operation on an East Texas virgin `straight run lube distillate stock, the West Texas cracked oils gave ahigher viscosity index improvement per stage of extraction and a lower pour point at similar-'dewaxin'g conditions. Thus the cracked oils are` *easier tov extract and dewax than straight, run (virgin) lube stocks.

Although residue stocks are advantageously cracked at low conversion in the production of lubricating oils, ac cording to one embodiment of this invention, other heavy oil stocks, such as the heavy Idistillate fractions usually obtained by vacuum llashing of topped crudes in the preparation of conventional catalytic cracker feed stocks, yield increased amounts of lubricating oil components at low conversion cracking, generally not over about 45% conl version (to gas and gasoline up to 450 F.),'and preferably no higher than about 40% conversion, as compared -to the yield at high conversions such as from 55 to 65% as used conventionally in catalytic cracking for the production of motor fuel. For example, whereas the heavy catalytic cracking gas oil (HCCGO) from a conventional commercial operation at 62% conversion yielded only about 6% wt. of a 100 SUS viscosity at 100 F. railnate (basis HCCGO), cracking at 53% conversion yielded a substantially larger proportion of about 20% wt. (basis HCCGO) of corresponding 100 SUS at 100 F. rainate lube.

As already indicated, only a relatively small proportion of high viscosity lubricating oil is recoverable from the usual catalytically cracked gas oil, which is because of the high level of conversion maintained to produce the maximum of motor fuel. Furthermore, the recoverable lubricating oil is usually in the low viscosity range of about 100 SUS at 100 F.

It has been found that larger yields of the low viscosity oil, as well as substantial proportions of higher viscosity oils are recoverable from the gas oils produced from dispersed-catalyst-phase riser cracking at lower conversions of 30% to 45 such as 37% and 42%, as compared to those at conventional plant conversions of about 55% and 62%. This is demonstrated by the data in Table IV, which give the results of lubricating oil recovery from dispersed-catalyst-phase riser cracking of a heavy llasher tops (HFT) of a West Texas crude (West Texas H-FT). The data show that the 765 F.{ fraction from the less severely cracked oils can be processed to yield considerably larger proportions of medium-viscosity oil (approxi mately 200 SUS viscosity at 100 F.) of high viscosity index.

TABLE IV Lubricating oil by low conversion catalytic cracking of West Texas heavy fiasher tops e Single-stage ghenol extraction at 130 F. with solvent-to-oil ratio o( 1.4, yield basis c arge to extraction.

b Percent Wt. heavy flasher tops to catalytic cracking.

Thus, according to the data in Table IV, not only is a larger yield of waxy raflinate obtained at the lower conversions of 37 and 42%, but the net yield of dewaxed oil (raffinate) is substantially higher than at the higher conversion of 53% while the viscosity index is essentially the same. For instance, the yield of 233 SUS Viscosity oil of essentially 100 V.I. dewaxed oil at 42% conversion was about 70% greater than of 194 SUS viscosity dewaxed oil at 53% conversion, based on the same feed stock to the catalytic cracking.

These data may be compared with data on the extraction and dewaxing of the same flasher tops, without the cracking, given in Table V.

TABLBV' -Extractiotz of West Texas 765 F,.}V fraction of heavy flasher tops Thus, even at a solvent-to-oiliratio of three,rthe vis-v cosity index was only about r89, whereas 'with the lowconversion cracking, a viscosity index of 100 was obtained with a ratio of only about 1.4.

Composition datav for the 765 R+ fraction of the heavy flasher tops, representing 31% weight of the total heavy asher tops, and for the 765 R+ distillate fractions from the products of 37%, 42% and 53% conversion catalytic cracking off the total heavy asher tops are given in Table VI.

p TABLE v1 A Composition of medium viscosity lube feed stock 7659 Fri- Fraction from 765 F.+ Riser Cracking of HFT Fraction i of HFT 37% 42% 53% Conv. Conv. Conv.

Alkenes v 15. 7 26.2 25.3 20.8 Non-Condensed Cycloalkanes 26. 9 31. 4 30. 6 A 24. 7 Condensed Cycloalkanes 16. 3 16. 4 17.0 14.0

Alkyl Benzenes 10.3 3.7 3.0 3.9 Monocyclic Aromatic Condensed with Cycloalkanes 9. 2 1.1 0. 9 1. 3

Total Monocyclic Aromatics. 19. 5 4. 8 3. 9 5.2

Polycyclic Aromatics 15.3 1l. 8 13. 7 17. 7 Sulfur Compounds 6. 3 9. 4 9. 5 17. 6

Total Polycyclic Aromatics i Y 'y and Sulfur Compounds. 21. 6 21.2 23. 2 v 35. 3

Yield of 765 F.+ Fraction, Basis oi HFT, Percent wt 31.0 13.0 9. 1 8.2 Yield of 765 F.-| Saturates,

Basis of HFT, Percent wt. 18. 3 9. 6 6. 6 4. 8 Yield oi 765 F.+ Alkyl Benzenes,

Basis HFT. Percent wt 3. 2 0.5 0. 3 0. 3 Yield oi 765 F.|- Condensed Cy cloalkyl Benzenes, Basis HFT, t Percent wt 2. 9 0. 2 0. 1 0. 1

The data in Table VI show that the conversions of both the monocyclic aromatic types tend to be more selective relative to saturates at the lower conversion (37%) than at the higher (53% The conversions for the two' types'of monocyclic aromatics fractions are about 85% and at an overall conversion of 37%. e Also, at 37% conversion, the retention of high boiling .saturates was about 52%, while at 53 conversion, saturates as well as aromatics had undergone a high degree of conversion. These data show that the most beneficial effects of cracking on extraction selectivity are realized at conversions well below those of conventional catalytic cracking operations. The data in Table VI show that at low conversions of the order of not over about 40% wt., such as about 37% wt., the reduction in solvent-to-oil ratio require ments occurs as a result of destruction of condensed monocyclic aromatics and alkylbenzenes. The data also indicate that at the higher conversion (5 3 the solventto-oil ratio requirement should be expected to increase because of the increased amount of polyaromatics in the 765 R+ fraction of the cracked gas oil. f

It is also to be seen from the'data in Table VI that,v

whereas the yield of the 765 F.| Vfraction from the fraction (31% wt.) of` the heavy flasher tops, the yield of the 765 R+ fraction from the cracking to 53% conversion was only 8% basis heavy asher tops, being about 74% lessthan the 765 F.l fraction of the heavy flasher tops. Furthermore, the hydrocarbon type composition data in Table VI showthat at a conversion of 37 wt., the ultimate yield of medium-viscosity rainate (saturates plus monocyclic aromatica) is 79% wt. of the V765 E+ fraction from cracked gasoil compared-to 78% wt. of this fraction from the heavy ash'er tops. This ultimate yield-of ranate fromthe cracked gas oil is similar to the- 81% wt. ultimate yield of rathnates from an East Texas high viscosity index lube crude 250 distillate fraction and to the 82% Wt. yield from a West Texas Ellenberger high viscosity index lube crude 250 distillate fraction. On the other hand, ultimate raffinate yield is lower for the cracked' gasoil obtained at high levels of conversion, being only 65% wt. at 53% wt. conversion.

The increase in concentration of saturates in the rainates, and the decrease in relative cncentration of condensed cycloalkanes in the saturates as a result of the cracking, gives dewaxed oils of unusually high isoparain content. This is shown by the data in Table VII, which compares the composition data of the dewaxed rainate from the cracked gas oil at 37% conversion and conventional dewaxed lube ratnates from commercial processing of East Texas (ET) and West Texas Ellenberger (WTE) lube crude distillates.

TABLE VII Compositions of dewaxed oils from various sources Dewaxed Raflnate from 765 Dewaxed Dewaxed F.+ Frac- Ranate Rafnate tion from from ET from WTE Cracked 250 Dis- 250 Ds- Heavy tlllate b tillate b Gas Oil,l 37% Conv.

Alkanes 19. 8 16. 7 12.8 Nonondensed Cycloalkanes 40. 2 36. 0 38. 4 Condensed Cycloalkanes 23. 8 29. 5 19. 4

Total Saturates 83. 8 82.2 70.6

Alkyl Benzenes 3. 3 5. 7 8.0 Monocyclic Aromatics Condensed with Cycloalkanes 1. 4 7. 7 10. 6

Total Monocycllc Aromatics 4. 7 13. 4 18.6

Polyeycllc Aromatics 7. 7 4.0 9. 3 Sulfur Compounds 3. 8 0. 4 1. 5

Total Polycycllc Aromatics and Sulfur Compounds 11.5 4. 4 l0. 8

Viscosity Index 100 93.8 94. 3

l From one-stage batch extraction.

Commercial extraction, continuous multistage.

The foregoing data have demonstrated that a reduced crude oil containing thermally unstable aromatic components, which are readily cracked with the formation of highly carbonaceous materials, can be advantageously cracked under low conversion conditions, especially over a cracking catalyst of relatively low activity, to produce a product from which an enhanced yield of high viscosity index lubricating oil can be obtained by distillation and extraction of a suitable distillate fraction thereof. The conversion may be as high as about 45%, preferably no higher than about 40% but lower conversions produce a largerproportion of high viscosity index components of lubricating viscosity. The conversion in general will be at least about and usually will be at least about 20%, preferably at least about 25%.

The amount of unstable highly aromatic material present in the'il stock may vary considerably in amount or 'chemical constitution, from essentially zero as in the case ofthe dashed distillate to as much as 20-40% in the case of asphaltic reduced crudes. In the case of asphaltic reduced crudes, not only will asphaltenes which are present be decomposed in part to more highlyy carbonaceous materials, but portions of alkylated polyaromatics present will be dealkylated and condensed to asphaltenes. Y Even in the case of heavy distillate aromatic oils, which contain more stable alkylated polyaromatics, they will bel dealkylatedV with partial condensation of the pol-yaromatics-nuclei to asphaltenes and more highly carbonaceous materials; even to coke.

The low-conversion cracking operation and recovery of lubricating, oil from distillate oil therefrom is particularly applicable to crude oils, or residual fractions therefrom, which contain a substantial amount of metal compounds, which are known to exert an inactivating eiect on the usual cracking catalysts.

Y The low-conversion catalytic cracking can be carried out in a fluidized catalyst system, whether dense phase or disperse phase, or a non-fluidized catalyst system, whether fixed bed or moving catalyst bed. Instead of using an active cracking catalyst, the conversion can be essentially thermal, and especially as in a iluid coking operation, wherein the heavy residual oil is partially thermally cracked by means of a mass of hot particulate coke to carbonize the less thermally stable materials and to distill off both initially present and formed distillate oil components.

The temperature of the low conversion cracking may range from about 480 C. to 610 C., depending on the thermal instability of the more susceptible constituents, while a temperature of from 510 C. to 540 C. is generally preferred.

The foregoing description of the invention will be more readily understood by a description of the practice thereof made with reference to the accompanying drawing. A high boiling petroleum distillate, such as a vacuum llashed distillate or a reduced crude, as conventionally produced is subjected to a low conversion catalytic cracking, as by a conventional catalytic cracking operation or as by a catalytic decarbonization in Zone A. The cracked products are then fractionated by a conventional method such as by fractional distillation in a fractionation zone B with the separation of gas, light distillate fractions and a residual or heavy gas oil distillate fraction. The residual or heavy gas oil fraction is then transferred to solvent extraction zone C wherein it is suitably solvent extracted with a conventional selective solvent, such as phenol, furfural, and the like. The waxy rainate produced thereby is then suitably dewaxed in dewaxing zone D by a conventional dewaxing process such as a solvent dewaxing process. The dewaxed oil and the wax are thereby separated and recovered as separate products for utility as desired.

I claim as my invention:

1. A process for the production of a mineral lubricating oil of high viscosity index which comprises: (l) subjecting a high molecular weight petroleum oil containing a substantial proportion of alkylated polycyclic aromatic asphaltene-precursors to low conversion cracking of not over about 45% conversion severity to obtain a cracked product containing a substantial proportion of naphthenic hydrocarbons, (2) separating oil as distillate from formed carbonaceous deposits, and (3) recovering lubricating oil components from the distillate as a solvent extraction rainate having a viscosity of at least about Saybolt Seconds Universal at 100 F.

2. A process in accordance with claim 1, wherein the high molecular weight oil is a crude oil flashed distillate and the low conversion cracking is a catalytic cracking over a catalyst at not over about 40% conversion.

3. A process for the production of a mineral lubricating oil of high viscosity index which comprises: (1) subjecting a reduced crude oil containing a substantial proportion of alkylated polycyclic aromatic asphaltene-precursors to low conversion catalytic decarbonization of less than about 55% conversion severity with the product of said decarbonization containing a substantial proportion of naphthenic hydrocarbons, (2) separating oil as distillate from formed carbonaceous deposits, and (3) recovering lubricating oil components from the distillate as a solvent extraction rainate.

4. A process in accordance with claim 3, wherein the solvent extraction rainate isdewaxed to produce a de- Waxed raiinate.

5. A process in accordance with claim 3, wherein the catalytic decarbonization is carried out with a solid hydrocarbon-cracking catalyst of low cracking activity.

6. A process in accordance with claim 3, wherein the catalytic decarbonization is carried out in the presence of a solid hydrocarbon-cracking catalyst of low cracking activity in a catalyst disperse phase cracking zone.

7. A process for the production of a mineral lubricating oil from an asphaltic reduced crude which comprises: (1) subjecting the reduced crude to catalytic cracking in a disperse phase cracking zone with a siliceous cracking catalyst at about 950 F. and about 37% conversion level to obtain a cracked product containing a substantial proportion of naphthenic hydrocarbons, (2) separating catalyst and formed carbonaceous deposits thereon from a high boiling 765 R+ distillate fraction, and (3) extracting said distillate fraction with a selective solvent for l0 aromatic hydrocarbons and producing a highly saturated raidnate fraction of high viscosity index and lubricating oil viscosity.

8. A process for the production of a mineral lubricating oil from an asphaltic reduced crude which comprises: (l) subjecting the reduced crude to catalytic cracking in a disperse phase cracking zone with a silica-alumina gel cracking catalyst containing 10-15% alumina and having a surface area of about 76 square meters per gram at about 950 P. and about 37% conversion level to obtain a cracked product containing a substantial proportion of naphthenc hydrocarbons, (2) separating catalyst and formed carbonaceous deposits thereon from a high boiling 765 R+ distillate fraction, and (3) extracting said distillate fraction with a selective solvent for aromatic hydrocarbons and producing a highly saturated ranate fraction of high viscosity index and lubricating oil viscosity.

References Cited in the le of this patent UNITED STATES PATENTS 2,616,836 Schmidt Nov. 4, 1952 2,660,552 Blanding Nov. 24, 1953 2,660,553 Knox Nov. 24, 1953 2,731,397 Erickson Ian. 17, 1956 

8. A PROCESS FOR THE PRODUCTION OF A MINERAL LUBRICATING OIL FROM AN ASPHALTIC REDUCED CRUDE WHICH COMPRISES: (1) SUBJECTING THE REDUCED CRUDE TO CATALYTIC CRACKING IN A DISPERSE PHASE CRACKING ZONE WITH A SILICIA-ALUMINA GEL CRACKING CATALYST CONTAINING 10-15% ALUMINA AND HAVING A SURFACE AREA OF ABOUT 76 SQUARE METERS PER GRAM AT ABOUT 950* F. AND ABOUT 37% CONVERSION LEVEL TO OBTAIN A CRACKED PRODUCT CONTAINING A SUBSTANTIAL PROPORTION OF 